The present disclosure relates to semiconductor apparatuses. When a photoresist (PR) strip process is performed on a semiconductor wafer, a photoresist layer on the semiconductor wafer may be removed from a surface of the semiconductor wafer. In a conventional photoresist strip process, Caro's acid is often used to strip the photoresist layer from the surface of the semiconductor wafer. However, Caro's acid is formed by the mixture of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2), so that Caro's acid is referred to as an environment-unfriendly liquid. After the photoresist layer is removed from the semiconductor wafer by Caro's acid, drained liquid may pollute environment.
Moreover, in previous processes, poly lines are formed on the semiconductor wafer and covered by the photoresist layer. When Caro's acid is in contact with the photoresist layer that covers the poly lines, the photoresist layer and Caro's acid induce poly damage due to violent reaction therebetween, such that poly peeling defects caused by the violent thermal stress of Caro's acid are formed on the semiconductor wafer. In addition, when the photoresist strip process is performed on the semiconductor wafer, the temperature of the semiconductor wafer may be gradually decreased from the center region of the semiconductor wafer to the edge region of the semiconductor wafer. Since a low stripping rate occurs at a low temperature region of the semiconductor wafer, edge remain defects may be formed on the edge region of the semiconductor wafer.